Lactic acid bacteria are capable of utilizing many different sugars as a source of carbon and energy (De Vos W. 1996. Antonie van Leeuwenhoek 70: 223). In a significant majority these sugars are monosaccharides or disaccharides. The ability of lactic acid bacteria to catabolize carbohydrates is widely used in biotechnological processes linked with food production (Libudzisz Z., Walczak P. and Bardowski J. (ed.), 1998. Lactic Acid Bacteria—classification, metabolism, genetics, application. (In polish) Monographies, Lódź; Aleksandrzak T., Kowalczyk M., Kok J., Bardowski J. 2000, Food Biotechnol. 17: 61, Elsevier Science B. V., Amsterdam). One of these processes is the production of fermented milk products. The main sugar in milk is lactose, which catabolism is a feature rather commonly present among lactic acid bacteria (Bardowski J. 1995. Przeglad Mleczarski 11: 315; Van Rooijen R. J. 1992. Lactose catabolism in Lactococcus lactis. Ph.D thesis, Wageningen, The Netherlands).
Yet another natural source, besides milk, of food production are plants. These biotechnological processes are frequently conducted with the use of lactic acid bacteria. However, in plant material, differently than in milk, polysaccharides such as cellobiose or starch are present. Thus, in the microbial conversion of plant material these microbials are incorporated which have either cellulolytic or amylolytic abilities. Lactic acid bacteria lack the ability to degrade cellulose.
However, the ability to degrade starch is, in this group of bacteria, a feature limited basically to a few strains of the Lactobacillus genus (cit. after Giraud E., A. Chapailler and M. Raimbault. 1994. Appl. Environ. Microbiol. 60: 4319). Some of these bacteria, belonging to the L. plantarum, L. amylophilus, or L. amylovorus species produce α-amylase (Fitzsimons A. and O'Connell. 1994. FEMS Microbiol. Letts. 116:137; Pompeyo C C., Gomez M S., Gasparian S., J. Morlon-Guyot 1993. Appl. Microbiol. Biotechnol. 40: 266).
It has been determined that besides strains from Lactobacillus genus, some strains of Lactococcus genus, naturally existing in the environment, also demonstrate this ability since strains which degrade starch were found among Lactococcus strains isolated from natural habitats (Domań M., E. Czerniec, Z. Targoński and J. Bardowski. (2000), Food Biotechnology 17:67, Elsevier Science B.V., Amsterdam).
Unexpectedly, it has been discovered that also other strains, especially from the Lactococcus lactis species, after introducing a specific gene structure according to the invention, are capable of producing a novel amylolytic enzyme which is encoded by this gene and which is secreted into the environment.